In a wireless communications system, a power amplifier is disposed at a front end of a transmitter, where a main function of the power amplifier is to implement amplification of a signal and meet a power requirement of sending a signal by the system. To ensure modulation precision and cause no interference with another system, a relatively high requirement is raised for a linearity technology of the power amplifier. Although the power amplifier and a related technology have always been a research focus in the communications field, requirements for the power amplifier are still centering around two aspects: efficiency and linearity, which mainly relate to various architectures of the power amplifier, various technologies of the power amplifier, and various algorithms that are of the linearity technologies and corresponding to the power amplifier. For example, a Doherty technology gains a great success in a practical application of the power amplifier. By using this technology, high efficiency can be provided, and a requirement of the system can be met by improving linearity by using a digital predistortion technology.
In an existing dual-input Doherty architecture that is based on and derived from a Doherty power amplifier, as shown in FIG. 1, a signal occupying a frequency band is divided into two channels of signals after being input from an input end, one channel of signal passes through a digital predistortion module, a digital-to-analog converter, and a peak power amplifier, the other channel of signal passes through a digital predistortion module, a digital-to-analog converter, and a main power amplifier, the two channels of signals are converged after being output by the peak power amplifier and by the main power amplifier, and the two channels of signals are matched by a matching module and then are output to a load apparatus. By using the dual-input Doherty architecture, an input impedance matching of the Doherty power amplifier can be improved, precision that cannot be reached by commissioning an analog power amplifier can be provided in the digital field, and load pulling of the Doherty power amplifier can be achieved with a high-precision time delay and phase.
As communications technologies develop, technologies such as a multiband technology and an ultra wideband technology raise a higher requirement for a power amplifier. Consequently, there is a great difficulty in considering both the efficiency and the linearity in the power amplifier architecture shown in FIG. 1. For example, the power amplifier architecture shown in FIG. 1 may be capable of meeting a requirement of a signal A in a frequency band f for aspects of efficiency and linearity, but has difficulty in meeting a signal B in a frequency band f for aspects of efficiency and linearity, and vise versa. If the power amplifier architecture meets requirements of both the signal A and the signal B, efficiency is very low, which brings a great difficulty in a system design.